Almost all modern day automobiles include a powertrain that is comprised of an engine and/or motor in power flow communication with a final drive system via a multi-speed power transmission. To operate properly, the traditional power transmission requires a continuous supply of pressurized fluid, such as conventional transmission oil. The pressurized fluid may be used for such functions as cooling, lubrication, and torque converter operation. It is well known that the lubricating and cooling capabilities of transmission oil systems greatly impact the reliability and durability of the transmission. Additionally, multi-speed power transmissions require pressurized fluid for controlled engagement and disengagement, on a desired schedule, of the various torque transmitting mechanisms that operate to establish the speed ratios within the internal gear arrangement.
The transmission's lubricating and cooling capabilities tend to degrade with transmission operation and over time. Contamination of the oil by water, particulate matter, such as dust or carbon, and oil degradation by-products affect the ability of the transmission oil to lubricate, cool, and protect critical transmission parts. Accordingly, most original equipment manufacturers (OEMs) provide guidelines for determining when the transmission oil should be changed. Such guidelines are typically stated with respect to a measurable period of operation or a period of time.
Though most transmissions have associated guidelines for the frequency of oil changes or service, more frequent changes may be required if the transmission is subjected to extreme operating conditions which may effect high levels of contamination or overheating. For instance, it has been found that excessive degradation of the transmission oil occurs at high temperatures. At elevated transmission oil temperatures, antioxidants in the oil become depleted and the oil becomes more viscous and acidic due to increased oxidation. Depending upon the transmission operating conditions, the oil change interval may be less than 50 percent of traditional guidelines, or may exceed the guidelines by 200 percent or more.